groundstation workshop gunther dice
TRANSCRIPT
“High Data-Rate” Communications for DICE
Jake Gunther, Charles Swenson, Chad Fish Utah State University & Space Dynamics Laboratory
[email protected] April 23, 2013
2
Dynamic Ionosphere CubeSat Experiment (DICE)
Cadet Radio
Langmuir Probe (+Z)
Langmuir Probe (-Z)
Magnetometer
Electric field
• DICE 70 Hz Science – 10.28 kbits/s
• DICE 35 Hz Science – 5.24 kbits/s
4
Store and Forward Fundamentals
Onboard Instruments
Spacecraft Memory Rcollected
Rtransmitted
Factor of Safety
10° Horizon
5
What does this mean?
• DICE-Wallops operates on a 8 hour work day 5-days/week – 1/α ≈ 25% (factor of safety of 4)
• Automated Ground Station – 1/α ≈ 100%
• DICE 70 Hz Science – 10.28 kbits/s
• DICE 35 Hz Science – 5.24 kbits/s
DICE Telemetry SystemTransmitted Rate Factor Collection Rate Samples Samples s/Image km/image
Mbits/s % kbits/s Hz m s km2.63 25% 6.58 411 18.3 638 47842.63 100% 26.30 1644 4.6 159 11965.00 25% 12.50 781 9.6 336 25175.00 100% 50.00 3125 2.4 84 62910.00 25% 25.00 1563 4.8 168 125810.00 100% 100.00 6250 1.2 42 315
16 Bit InSitu 512x512x16 image
Assuming 1% Access to Satellite
6
Regulations on 460 to 470 MHz
• 5.289 Earth exploration-satellite service applications, other than the meteorological-satellite service, may also be used in the bands 460-470 MHz and 1690-1710 MHz for space-to-Earth transmissions subject to not causing harmful interference to stations operating in accordance with the Table.
• US201 In the band 460-470 MHz, space stations in the Earth exploration-satellite service may be authorized for space-to-Earth transmissions on a secondary basis with respect to the fixed and mobile services. When operating in the meteorological-satellite service, such stations shall be protected from harmful interference from other applications of the Earth exploration-satellite service. The power flux-density produced at the Earth’s surface by any space station in this band shall not exceed -152 dBW/m²/4 kHz.
10 MHz Bandwidth available
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1.56 dB Gain
1.39
1.18
0.91
0.52
-3.5
With FEC the Downlink Data Rate is 2.63 Mbps
DICE Telemetry Systems (3 Mbit/s)
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Telemetry COTS: L3 Cadet Radio
• UHF or S-Band
• Downlink:1-20 Mbps
• Uplink: Up to 250 kbps
• Size: 2.7" x 2.7" x 0.53"
• Weight: 7.6 oz
• Transmit: 8-12 Watts
• Receive: 0.3 Watts
• Memory: 4 GB Flash
Source: http://www2.l-3com.com/csw/ProductsAndServices/DataSheets/Cadet_Nanosatellite_Radio_WEB.pdf
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DICE SDR
WBX 50-2200 MHz
BPF + LNA Ethernet
RF Front End ADC + DDC Digital Signal Processing • Detection • Interference cancel. • Doppler correction • Synchronization • Demodulation • FEC decoding • Back-end services • MSQL database
DICE Software Defined Radio (SDR) • Too much DSP pushed on to PC • PC could not meet real-time schedule • Record data during overpass • Post-process data
Real-time processing needs • Move DSP back to FPGA or add DSP/GPU • Move away from USRP-based solution: not enough user
space on FPGA
USRP N210
10M samp./sec. I/Q data
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Interference at Wallops Site Interference at SRI Site
Signal
460 to 470 MHz Band
With Interference Cancelation
460 to 470 MHz Band
Interference
11 time domain
Cognitive Radio
• Be proactive toward interference rather than reactive
• Concept: Divide spectrum into 100s or 1000s of narrow spectral sub-channels
• Cognitive radio 1. Ground station measures interference in
each sub-channel 2. List of clear channels sent to spacecraft 3. Spacecraft transmits on clear sub-channels
• Makes best use of available bandwidth
• Achieves highest data rate
• FEC across sub-channels to overcome unanticipated interference
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Farkle Data Recovered
• 5.13GBytes of data recovered and stored in a MySQL database
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
Mby
tes R
ecov
ered
Date
Farkle Data Downloaded
Dish Tracking Problems Power Issues/ On-Board Computer Freeze
Ground Station Upgrade
14
Yahtzee Data Recovered
• 3.26GBytes of data recovered and stored in a MySQL database
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
Mby
tes R
ecov
ered
Date
Yahtzee Data Downloaded
Dish Tracking Problems Power Issues/ On-Board Computer Freeze
Ground Station Upgrade
15
Odds & Ends
• 26Terabytes of raw I/Q samples from USRP have been stored at SDL
• Ran a 2 part Science campaign with ISR groups around the world in early March
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DICE Magnetometer Data
0 500 1000 1500 2000 2500 3000-8
-6
-4
-2
0
2
4
6
8x 10
4
Time (Sec) since 22:19:24.212984
Mag
netic
Fie
ld (n
T)
Farkle Science Magnetometer 05/22/2012 22:19:24.212984 UT
BxByBz|B|
400 nT